Measurement-While-Drilling (MWD) systems are well-known in drilling technology. The term “measurement-while-drilling” encompasses a wide array of different tools and instruments having a corresponding wide array of functions. For purposes of example in this disclosure, however, MWD refers to navigational tools (or “directional tools”) that monitor the direction and rate of travel of the tool face during directional drilling operations. Such MWD tools typically include magnetometers and/or accelerometers (colloquially known collectively as a “directional package”) for measuring travel and direction of the tool face in relation to vectors of known directional forces such as the Earth's magnetic and gravitational forces. It will be appreciated throughout this disclosure, however, that even though such directional MWD tools are used by way of illustration, this disclosure is not limited to such directional MWD tools in the application of the orienting hanger device also disclosed herein.
MWD tools typically take the form of a substantially uniform cylinder, including a cylindrical sonde containing the directional package, plus other cylindrical components containing items such as batteries and related electronics. The tools' cylindrical shape generally facilitates deployment in a specially-configured section of drill collar to form a “sub” that may be inserted into a conventional drill string. MWD tools may be retrievable or non-retrievable, as described further on in this background. Where retrievable, their cylindrical shape enhances such retrievable deployment.
Directional sensitivity is enabled on the MWD tool, at least in part, by identifying a “high side” on the outside of the tool. More precisely, the “high side” is a radial orientation (or radial azimuth) marked on the outside of the tool that the directional sensors deployed on the inside of the tool will recognize as “top dead center” or “zero degrees tool face”. Part of the job of “making up” a bottom hole assembly (BHA) prior to directional drilling includes orienting the MWD tool, within its corresponding sub, so that the high side of the tool is directionally aligned with the intended zero degrees on the tool face. Advantageously the high side of the tool is exactly directionally aligned with zero degrees on the BHA tool face. If not exactly directionally aligned, the misalignment must be precisely known so that appropriate corrections may be made by software in the directional package.
In directional drilling operations using a bent sub, a scribe line on the bent sub will indicate zero degrees tool face. Similarly, in directional drilling operations using a steering tool, the steering tool will have some external physical reference mark indicating its intended zero degrees tool face during use. Conventionally, the scribe line or other reference mark is transferred externally to the collar housing the directional package using, for example, a chalk line, a laser, visual alignment, or similar method. The MWD tool is then oriented within its collar so that its high side aligns with the scribe line or other reference mark as transferred onto the collar.
As noted above, MWD tools come in both retrievable and non-retrievable varieties. “Retrievable” refers to the MWD tool being specially configured to be retrievable from the drill string without tripping the drill string out of the well. The most common retrievable deployment is to locate the MWD tool sub at the very top of the tool string in the BHA, just below the bottom of the drill pipe string, where the top of the MWD tool can be accessed by a wireline run through the hollow drill pipe string from the surface. The end of the wireline provides a hook device which can be attached to a latching device provided on the top of the MWD tool. Once hooked on, the MWD tool can be pulled up and retrieved from inside its collar.
Also as noted above, such a retrievable MWD tool is conventionally cylindrical so that it may be more easily withdrawn from within its collar. Conventionally, external bow springs are provided on the outside of the cylindrical MWD tool, which compress as the MWD tool is inserted into a hole-like receptacle within the collar. The bow springs hold the MWD tool in place in its receptacle, advantageously without rotation with respect to the collar, so to preserve alignment with zero degree tool face of the BHA as described above. External rubber fins on the tool exterior can also be used to position and stabilize an MWD tool (see, e.g., The Pathfinder HDSR). However, if fins are used, a separate internal collar contact is needed to complete the electrical connection of the EM tool. Regardless of the method used, to retrieve conventional tools, the pull on the MWD tool must be sufficient to withdraw the MWD tool longitudinally from its receptacle against the urge of the bow springs.
A primary advantage of retrievable MWD tools is that they are, as noted, retrievable from the drill string without tripping the drill string out of the well. Tripping is a time-consuming process, and to be avoided during drilling operations whenever possible. MWD tools may need to be brought back to the surface before drilling operations are complete for any one of a number of reasons. These reasons include the MWD tool requiring service, or perhaps running out of battery power, or requiring a download of locally-stored data, or even malfunctioning. All of the above tasks may be accomplished without tripping by using a retrievable MWD tool. Furthermore, in situations where the BHA has become stuck in the borehole, it will be appreciated that retrievable MWD tools may be more easily salvaged.
Retrievable MWD tools have a number of disadvantages, however, as compared to non-retrievable MWD tools. In order to promote retrievability, retrievable MWD tools are not easily linked to other downhole measurement devices that may also be located in the tool string in the BHA, such as Logging-While-Drilling (LWD) tools or other MWD tools. Thus, telemetry capability as conventionally found on MWD tools may not also be used in conjunction with such other downhole tools. Further, the conventional bow spring deployment of retrievable tools, as described above, causes the MWD tool to be rotationally immobilized with respect to its surrounding collar only by the force reacting to compression of the bow springs. The potential for differential radial movement between MWD tool and the surrounding collar thus exists, potentially brought about by vibrations caused during drilling operations. In particular, the high vibrations caused by air drilling have an increased potential to undermine the alignment of a conventionally-deployed retrievable MWD tool.
Of course, the disadvantages of conventional retrievable MWD tool deployments as described immediately above may be addressed by deploying a conventional non-retrievable MWD tool. Non-retrievable MWD tools may be mounted more robustly and integratedly in the tool string in the BHA without concern for retrievability.
It will therefore be appreciated from the foregoing background disclosure that there are some drilling applications in which a retrievable MWD tool may be preferable, and other applications in which a non-retrievable MWD may be preferable. From a tool supplier's point of view, it is not always optimal to keep a large inventory of both retrievable and non-retrievable MWD tools. Inventory and manufacturing efficiency can be enhanced when retrievable MWD tools can be optionally converted to non-retrievable MWD tools, thereby enabling use of the same tools in both retrievable and non-retrievable MWD drilling applications.
Techniques are currently known for converting retrievable MWD tools into non-retrievable MWD tools. However, these current techniques tend to be rather cumbersome and unreliable. The conversion is typically accomplished first by threading and torquing one or more orientation devices to the top and/or bottom of a retrievable MWD tool. The orientation devices are generally cylindrical transition pieces which (1) re-dimension the MWD tool assembly to be suitable for being received into a non-retrievable MWD tool mounting device (such as a suitably-configured length of drill collar), and (2) transfer the orientation reference line on the MWD tool onto a corresponding reference line on the mounting device, which can then be used for alignment with the scribe line on the bent sub during make-up of the tool string in the BHA. Adding the orientation devices(s) and the mounting device to the MWD tool thus requires addition of at least two (2) threaded/torqued connections. It will be appreciated that making these additional connections up is inefficient and cumbersome in many applications. Further, it will be appreciated that loss of torque and loosening of the threaded joints during drilling operations will likely cause a misalignment of the MWD tool's directional sensors with the tool face of the BHA.
Thus, there is a need in the art for a conversion device that quickly and nimbly converts a retrievable tool (including a retrievable directional MWD tool) into a corresponding non-retrievable MWD tool that may be mounted in a section of drill collar. The section of drill collar may then be placed in any desired position in the tool string in the BHA. The conversion device should avoid threaded/torqued connections that may loosen during drilling operations and possibly cause a misalignment in orientation of a directional MWD tool.
Advantageously the improved conversion device will accommodate EM MWD tools that include EM telemetry transceivers (and associated architecture and circuitry) on board. In such EM MWD deployments, the conversion device will enable optional mounting of the retrievable EM MWD tool in a gap sub.